1. Field of the Invention
The present invention relates to a plasma treatment apparatus for forming an active layer and a wiring over a substrate. Moreover, the present invention relates to a plasma generation unit of a plasma treatment apparatus for film formation, etching or surface modification.
2. Related Art
A thin film transistor (TFT) formed over a substrate having an insulating property is widely applied to an integrated circuit and the like. Especially, the TFT is used a lot as a switching element in a display portion of a thin display device represented by a liquid crystal television receiver or the like, and has been widely used for a portable terminal, a large-sized display device, and the like.
As for a display device using a conventional TFT, a film is formed over an entire surface of a substrate, and a TFT is formed by applying photolithography, etching, and ashing. More than half of these processes for manufacturing the TFT are often performed in vacuum equipment.
In recent years, a large-sized liquid crystal display device has been attracting a lot of attention. Accordingly, a size of mother glass is enlarged, thereby enlarging a size of vacuum equipment and requiring a larger-scale facility investment.
In such the situation, a plasma treatment can be performed with a glow discharge maintained without shifting to an arc discharge even under atmospheric pressure by using a method for applying a pulsed electric field as a plasma generating unit, which has been attracting a lot of attention in recent years.
In the case of generating plasma under atmospheric pressure, a particle is easily generated due to generation of high-density plasma. The particle is to be a cause of a defect such as a point defect or a line defect in a display portion of a display device.